Conventionally, there have been various types of touch panel devices. Especially, a capacitive touch panel device, which utilizes electrostatic capacitance, achieves greater convenience because an operator can carry out direct touch operation by the fingertip or can carry out touch operation with the use of a simple stylus pen that is made of an electrically conductive material.
In general, a capacitive touch panel device includes (i) a touch panel unit in which a plurality of drive lines (first electrode) and a plurality of sense lines (second electrode) intersect with each other (like grade separation) and (ii) a touch panel controller for controlling the touch panel unit. The touch panel controller applies driving signals to the plurality of drive lines and detects a touch location based on sensing signals (response signal) generated in the plurality of sense lines. Specifically, when an electrically conductive object approaches or makes contact with the touch panel unit, electrostatic capacitances generated at intersections of the plurality of drive lines and the plurality of sense lines are changed. From this, the touch panel controller detects a signal strength at coordinates of each of the intersections of the plurality of drive lines and the plurality of sense lines in the touch panel unit based on the sensing signals generated in the plurality of sense lines, and the touch panel controller can thus detect a touch location.
With regard to the touch panel controller for controlling a capacitive touch panel, various kinds of configurations have been proposed. For example, Patent Literature 1 discloses a touch detection device for improving an S/N ratio and detection accuracy in detecting a sensing signal. As illustrated in (a) through (d) of FIG. 11, the touch detection device of Patent Literature 1 includes n-pieces of driving electrodes E1 arranged in a scanning direction, a detection drive scan section 111, a plurality of detection electrodes E2, and k-pieces of voltage detectors DET. The detection drive scan section 111 (i) selects, from the n-pieces of driving electrodes E1, an AC (alternate current) driving electrode unit EU that contains sequential m (2≦m<n) pieces of driving electrodes and (ii) drives the AC driving electrode unit EU with an AC voltage. The detection drive scan section 111 carries out shift operation in which the selection target is changed in the scanning direction. Specifically, the detection drive scan section 111 repeats the shift operation such that at least one driving electrode is selected in both of any sequential two shift operations. Every time the detection drive scan section 111 carries out the shift operation, each of the voltage detectors DET compares an electric potential of a corresponding detection electrode E2 with a predetermined threshold Vt.